In forestry, as well as in the building industry, many hand-held motor devices are driven by internal combustion engines due to the lack of electric power supply. Typical examples of such hand-held motor devices are abrasive cut-off machines which are used, for example, for laying floor slabs made of concrete or stone. Likewise, chain saws for professional use are often driven by internal combustion engines.
It is only natural that a large amount of abrasive dust is produced when these motor devices are used. The internal combustion engine at the device suctioning this abrasive dust, which can, for example, consist of concrete particles, causes an increased wear of the parts of the internal combustion engine that are in contact with the dust. The piston and the cylinder barrel are particularly subject to wear in an internal combustion engine. In two-stroke engines, which are advantageous in hand-held motor devices because of their simple and light design, the crankcase, the crankshaft and their bearings also come into contact with the dust contained in the intake air. In internal combustion engines operating according to the four-stroke principle, the gas exchange valves and their valve guides are in contact with the intake air, and accordingly wear quicker if this intake air contains abrasive particles.
In order to reduce this wear, it has long been usual to provide an air filter which cleans the drawn in combustion air and filters out as many particles contained in the intake air as possible before said particles reach the internal combustion engine.
In practice, however, this objective can only partially be achieved because, firstly, the flow resistance of the air filter increases with increasing separation efficiency, and consequently the efficiency and the performance of the internal combustion engine decreases.
Moreover, the capacity of an air filter depends on its size. However, since the installation space available in hand-held motor devices is limited, the capacity of the air filter thus is also limited.
It has therefore been known from the prior art to provide a so-called cyclone separator upstream of the actual air filter. In a cyclone separator, coarse particles are removed from the intake air in that the intake air performs a circular movement and, owing to their higher density, the impurities are centrifuged to the outside and collected there. The required installation space increases because of this additional assembly.
Likewise, these cyclone separators in conjunction with an air filter that is installed downstream are further improvable with respect to separation efficiency and the required installation space.